1. Field of the Invention
The present invention relates to a muffler mounting structure of a vehicle, and particularly relates to a muffler mounting structure suitable for a straddle-type four-wheeled vehicle.
2. Description of the Related Art
FIG. 9 shows a body frame, an engine, an exhaust system, and the like of a conventional saddle-type four-wheeled vehicle described in U.S. Pat. No. 6,719,084. In FIG. 9, the body frame is provided with a box-shape main frame portion 201, and a rear frame portion 202 protruding rearward from the main frame portion 201. An engine 204 is for example a V-engine having a front cylinder 204a tilted forward and a rear cylinder 204b tilted rearward, and is arranged in the main frame portion 201. A muffler 205 is mounted on one side of the rear frame portion 202 in the lateral direction. A front-cylinder exhaust pipe assembly 210 connected to the front cylinder 204a of the engine 204, and a rear-cylinder exhaust pipe assembly 211 connected to the rear cylinder 204b are respectively extended rearward and connected to the muffler 205.
A muffler mounting plate 215 is fixed on the one side of the rear frame portion 202 by welding, and this muffler mounting plate 215 has a substantially vertical mounting surface, and a female screw portion (not shown). Meanwhile, a pair of mounted brackets 216, 216 protruding upward is formed in an upper end of the muffler 205. These mounted brackets 216, 216 respectively have mounted surfaces substantially parallel to the muffler mounting plate 215, and bolt insertion holes (not shown) passing through the mounted brackets 216, 216 in the lateral direction. The mounted brackets 216, 216 are fixed to the muffler mounting plate 215 by a pair of bolts 217, 217 inserted from the side (the left side).
As shown in FIG. 9, in a structure in which the vertical mounted surfaces of the mounted brackets 216, 216 of the muffler 205 are matched with the vertical mounting surface of the muffler mounting plate 215 of the rear frame portion 202, and fixed by the bolts 217, 217 from the side (the left side), the muffler 205 is easily oscillated in the front and rear direction during travel due to vibration of the vehicle and the like. Thus, moment is applied onto the bolts 217, 217 around axes of the bolts, so that the bolts 217, 217 are easily loosened. Therefore, there is a need for providing prevention of loosening and the like.
In a case where the bolts 217, 217 and the like are operated from the side of the vehicle, a rear fender, rear wheels, and the like can sometimes interfere with and complicate a mounting operation.